Maximum response of loblolly pine plantations to silvicultural management in the southern United States

Pine plantations in the southern US are among the most intensively managed forests in the world and their productivity has tripled over natural pine forests through application of intensive pine plantation establishment and management practices. As we are trying to increase carbon (C) sequestration through further enhancing pine plantation productivity by refinement of silvicultural regimes, whether a maximum productivity or the maximum potential C sequestration exists remains unclear. Our analysis of six long-term field trials indicated that a maximum productivity and a maximum response to silvicultural practices for loblolly pine (Pinus taeda L.) exist across the species geographic range in the southern US. The maximum response was inversely proportional to the base site quality, and silvicultural treatments never increased productivity above that maximum. Further analysis of loblolly pine culture and density studies demonstrated that the effects of planting density and cultural treatment intensity on biomass production strongly interacted with site quality in that lower quality sites responded more to silvicultural intensity than higher quality sites. The results highlight that we can optimize silvicultural prescriptions for specific sites by changing silvicultural intensity depending on the site quality.